Free standing and/or wall mounted display racks, with which the present invention has been found useful, are familiarly employed in self service stores for displaying and merchandising a great variety of consumer products. Many of such display racks provide a plurality of pegs from which packaged articles are suspended. In other instances heavy or bulky items are displayed on open horizontal trays or shelves usually supported by two or more cantilever supporting arms attached to vertical upright supports or, in other instances, attached to peg boards or peg bars. In general, experience has demonstrated that the typical known cantilever arm supported shelf systems are quite unstable and prone to accidental collapse or distortion, particularly if struck by a passing stock cart or bumped into by a customer. In other instances, it has been found that efforts to stabilize and rigidify the shelf supporting cantilever support arms has so complicated the means for securing them to the upright supports that their assembly and disassembly is prohibitively inconvenient and time consuming. Consequently, there exists a realistic need for an improved cantilever shelf mounting system, particularly useful for merchandise displays and like shelf uses.